1. Field of the Disclosure
Embodiments disclosed herein generally relate to tools, systems, and methods for the removal of obstructions, deposits and/or other debris in tubulars, wellbores, and other confined areas. Specific embodiments relate to a multifunctional cleaning tool for the cleaning of pipelines, especially long-extended and/or horizontal pipelines, and methods for using the same.
2. Background Art
A characteristic common to hydrocarbon production operations throughout the world is the eventual build-up of a wax or paraffin component of the hydrocarbons that deposits on the walls of a pipeline, and solidifies at low temperatures. Some of these waxes or paraffins deposit and/or solidify at temperatures in excess of 100 degrees Fahrenheit, which means the deposits will form on pipeline surfaces even at temperatures close to ambient. Once deposits form, the thickness of the deposit layer will increase over time, which causes, for example, increased pressure drop and/or decrease in desired flow rate in the pipeline.
A common example of where this situation is a frequent occurrence is in subsea production operations. In this instance, pipelines are used to connect subsea wellheads to one another and/or to surface facilities so that hydrocarbons may be produced and recovered from the subsea wells and transported therebetween. Additionally, longer pipelines are routinely used to transfer production fluids from offshore installations to shore. As relatively hot hydrocarbons are produced from subterranean formations up to the sea floor, and subsequently through pipelines extending along the sea floor, the relatively low temperature of the surrounding water cools the hydrocarbons. This cooling rapidly causes the wax, paraffin, etc. present in the hydrocarbons to deposit and enter the solid phase.
It is not uncommon for pipelines to have more than 90% of the flow area blocked with the built up layer of deposits. As a consequence, production operators see operation costs significantly increase over-budget. For example, pump capacities need to be increased to compensate negative effects, such as restricted flow due to reduced inner diameters of pipelines, increased wall roughness, and increased viscosity of the oil. In general, blockages in production or transfer lines are extremely costly because they reduce, hinder, and may even stop production.
As a result, strategies and techniques have been developed to limit deposit formation, as well as to clean affected pipelines (e.g., flow assurance). Most often, a deposit control strategy consists of removing the deposits from the wall of the pipeline. One well known method of treating deposit buildup in pipelines, as shown in FIGS. 1A and 1B together, is to insert a mechanical cleaning device called a “pig” into the flow stream and let the pig remove some of the deposits 199. A pig tool 100 typically entails a cylindrical or spherical body or housing 105 connected with cups 110 or other devices that will seal, brush, scrape, etc. against the internal diameter 133 of the pipeline 131, such that at least some of the deposits are mechanically removed as the pig 100 runs through the pipeline.
In a large number of cases regular pigging manages to keep the deposit formation within tolerable limits. As such, a regular pipeline maintenance program with pigs is normally prescribed as a preventative measure to reduce pipeline blockage, and is becoming more and more common today. However, the use of the conventional pig 100 is not without limitations.
One problem with using conventional pigs is that deposits 199, such as waxes and paraffins, are relatively soft and contain large quantities of oil. To some extent, the conventional pigs actually compress the deposits against the wall and squeeze the oil out, leaving a harder and stronger layer of deposits remaining.
A second problem is that when the layer of deposits 199 on the internal surface 133 of the pipe 131 is too thick, sloughing or shedding of the deposits may occur. For example, if the deposits 199 start to separate from the wall and continue to do so, the conventional pig 100 begins to literally form a block of deposit mass ahead of its end 109. This action drives more and more deposits off the wall 133 of the pipeline 131 until the pressure within the pipeline will no longer be able to move the pig 100 and the block of mass any further.
At that time the pipeline 133 is fully blocked, and the pig 100 cannot be moved by pressure from either end. An operator cannot increase pressure to move the pig from the rear because conventional pigs are not designed to withstand the extreme pressures, and the pig will blow apart. And an operator cannot increase pressure to move the pig from the front because the block of mass blocks flow.
In recent years, oil and gas operators have discovered a technique to aid pig deployment that includes the use a continuous length of flexible tubing with the pig attached at the distal end thereof. This tubing, which may be, for example, “coiled tubing,” utilizes a continuous length of up to 10,000 feet of flexible tubing stored on a reel. The continuous tubing is relatively flexible, and is typically rolled off a large reel (from a boat or other support structure) and into pipeline. Such conventional coiled tubing can be translated in and out of a wellbore or other vertical structure in a continuous manner. As such, the continuous tubing can be inserted into a pipeline and used to push or otherwise urge a pig through the line in instances where the required pressure would otherwise be too large for the pig too handle.
Be that as it may, large forces are often required to insert and withdraw extended lengths of continuous tubing into a pipeline that may be filled with hydrocarbons, solid deposits, and/or other materials. Moreover, coiled tubing operations are unusable for horizontal flow lines (e.g., transfer lines, etc.) of any significant length. When used in long horizontal lines, the continuous tubing becomes too horizontal, and as such the weight of the tubing acts against the internal surfaces of the pipeline, thereby creating frictional forces that impede the advancement of the tubing through the pipeline. The weight of the tubing may cause the tubing to rest on the inside of the pipeline, creating a resistance to moving the tubing relative to the pipeline, as well as damage to the wall of the pipeline and the tubing.
As a result, tubing conveyed systems may not be preferred in pipelines having long horizontal lengths because the weight of the tubing may hinder the travel of the pig and/or cause damage. Moreover, use of rigid tubing may be problematic in that the tubing may not be flexible enough to be inserted into pipelines that have bends or other tortuous pathways.
As such, it is not possible to effectively use conventional pig technology in long horizontal pipelines. The required pressure to run the pig completely through the pipeline becomes too great, such that the pig will blow apart, be destroyed, and/or rendered unusable. The cost to deploy tools with continuous tubing is very expensive, and the use of continuous tubing to aid in urging pigs horizontally is of no help because of the aforementioned problems and limitations.
Thus, there remains a need for a tool, system, and method for cleaning undesirable materials built-up, or otherwise collected, on the inside surface of pipelines. There is tremendous need for a tool and method for cleaning long-extended and/or horizontal pipelines, including lengths in excess of 10 miles, as well as a tool that may be deployed without continuous tubing. There is a great need for a tool that can withstand extreme pressures in order to run tether-free in pipelines when desired, and also have internal protection systems to prevent over pressurization of the tool.
There is a need for a multifunctional cleaning tool that may perform mechanical cleaning, as well as pressurized cleaning. There is also a need for a multifunctional tool that may perform downhole operations in addition to cleaning. As such, the current needs of the pipeline industry further require a tool that is multifunctional, cost-effective, and easy to manufacture and operate.